For a while I've been wanting a way for a program to find out if any of its
socket buffers were overflowing due to too much incoming traffic.  Finally, I
decided to code it up and try it out.

As it turns out, it was relatively simple to add, although it required the
addition of two new entries in sockios.h.

Basically, inside of sock_queue_rcv_skb() and sock_queue_err_skb() the receive
counter gets incremented unconditionally, and then if there is no free space in
the socket buffer then we also increment the counter for messages dropped due to
out of memory.

The stats are stored as part of a socket_stats struct, making it easy to add
other counters in the future.

To access and reset the counters, two ioctl commands were added to the socket
ioctl. GIOCSOCKSTATS is used to get the stats, while SIOCZEROSOCKSTATS is used
to reset them.  I haven't bothered with trying to reset them both atomically as
I don't think it's that critical.

The patch was coded and tested for 2.4.18, but it is known to at least apply
(with offsets) on 2.5.20.

Feel free to bash on it a bit, once the issues are worked out I'll submit to the
appropriate maintainer.

Chris
 
-- 
Chris Friesen                    | MailStop: 043/33/F10  
Nortel Networks                  | work: (613) 765-0557
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